High-pressure plasma burner

ABSTRACT

High-pressure plasma burner of the gas heater type includes a pressuretight arc chamber containing electrodes adapted to form an arc therein, flow discharge nozzle means for discharging from the arc chamber working gas heated and ionized therein by the arc, coolant channels located in parts of the arc chamber thermally stressed by the arc, the coolant channels being connected in a closed coolant loop, and a pressure transmitter and pressure line pressure transmittingly interconnecting the pressure tight arc chamber and the closed coolant loop.

{72] inventors RudolfGebel Tennenlohe; Helmut Forster, Neunkirchen, bothof, Germany [2]] Appl. No. 887,578

221' Filed Dec. 23, 1969 [45 Patented Aug. 24, 1971 [73] AssigneeSiemens Aktieugesellschaft 7 Berlin and Munich, Germany [32] PriorityJuly 1, 1969 [33] Germany [54] HIGH-PRESSURE PLASMA BURNER 6 Claims, 2Drawing Figs.

[52] U.S.Cl 219/121P, 219/75 [51] lnt.Cl 823k 9/00 {50] Field ofSearch2l9/l21,

[56] References Cited UNITED STATES PATENTS 3,360,682 12/1967 Moore219/121 X Primary Examiner-Clarence L. Albritton AssistantExaminer-Joseph V. Truhe I Attorneys-Curt M. Avery, Arthur E. Wilfond,Herbert L.

Lerner and Daniel J. Tick ABSTRACT: High-pressure plasma burner of thegas heater type includes a pressuretight are chamber containingelectrodes adapted to form an arc therein, flow discharge nozzle meansfor discharging from the arc chamber working gas heated and ionizedtherein by the arc, coolant channels located in parts of the arc chamberthermally stressed by the arc, the coolant channels being connected in aclosed coolant loop, and a pressure transmitter and pressure linepressure transmittingly interconnecting the pressure tight arc chamberand the closed coolant loop.

HIGH-PRESSURE PLASMA BURNER Our invention relates to a plasma burner ofthe gas heater typeand more particularly to such plasma burner having anarc chamber containing electrodes adapted-to form an arc therein, a flowdischarge nozzle for discharging from the arc chamber working gas heatedand ionized therein by the arc,

and coolant channels located in parts of the arc chamber thermallystressed by the arc, the coolant channels being connected in a closedcoolant loop.

Through special measures, plasma burners of the gas heater type can beconstructed as high-pressure plasma burners. Such plasma burners whichoperate at high pressure are suitable for supplying wind tunnels inexperiments of tests relating to space flight engineering, especiallyfor simulating reentry of missiles into the atmosphere of the earth.Furthermore, such plasma burners can be employed in chemical technology.

In high-pressure plasma burners, it has been conventional heretofore toraise the coolant pressure by means of pumps.

The invention of the instant application derives from the realizationthat when there is a coolant pressure below the operating pressure inthe arc chamber becauseof leaks in the thermally stressed parts thereof,ionized working gas or plasma can penetrate into the leaking ordefective part and can cause even greater damage. On the other hand, inorder to adjust the coolant pressure to a value above the operatingpressure in the arc chamber for high-pressure plasma burners,

considerable pumping expenditure is required and manifold difficultiesmust be overcome. In addition, further problems must be coped with whenstarting up and stopping the operation of the plasma burner.

It is accordingly an object of our invention to provide highpressureplasma burner which avoids the aforementioned disadvantages of theheretofore known plasma burners of this general type and which increasesthe efficiency and the relia- ,bility thereof. More specifically, it isan object of our invention -to provide such plasma burner wherein atstartup, during regular operation and at shutdown thereof, the coolantpressure is synchronized with the operating pressure in the arc chamber,and the pressure at each cooling location is maintained at leastslightly above the operating pressure within the arc chamber.

With the foregoing and other objects in view, we provide, in accordancewith our invention, high-pressure plasma burner of the gas heater typecomprising a pressuretight are chamber containing electrodes adapted toform an arc therein, flow 'discharge nozzle means for discharging fromthe arc chamber working gas heated and ionized therein by the arc,coolant channels formed in parts of the arc chamber thermally stressedby the arc, the coolant channels being connected in a closed coolantloop, and a pressure transmitter pressure line pressure transmittinglyinterconnecting the pressuretight arc chamber and the closed coolantloophThe coolant is thereby additionally continuously pressurized by theoperating pressure in the arc chamber. The pressure to be applied by thecirculating pump, and which reduces up to the return flow into the pump,can be kept relatively low.

Advantages of the plasma burner according to our invention is thatbecause the pressure difference between coolant and operating pressurein he arc chamber can be kept very small, the walls between the coolantchannels and the inner sides of the operating chambers are able to be ofthin-walled construction, which assures good cooling in addition to asaving of material. Also, in accordance with ,thexinvention', coolanthoses are installable inthe plasma burnercutside the range of the arcradiation, because compression of the hoses need not be feared. There isfurthermore assured that only coolant can escape at the leakagelocations in the thermally stressed arc chamber parts. Also, the coolantpump has to produce only the circulation work.

In accordance with another feature of our invention, we displaceablymount at least one of the two electrodes so as to be able thereby tovary the spacing between the electrodes, the

displaceable electrode being axially displaceable'for a given distanceand serving as a closure plate for closing an adjustment chamber havinga length correspondingto the given distance along which the displaceableelectrode is adjustable, the adjustment chamber and the arc chambercommunicating in pressure equilibrium with one another, motor drivenadjusting means in the adjusting chamber for adjustably displacing thedisplaceable electrode, and supply lines passing rigidly through anadjustment chamber wall.

Through such an adjustment chamber, according to the invention, which iskept at the same pressure as that of the operating space in the arcchamber, a pressure-relieved electrode displacement is attained, andsealing problems relating to mounting of the electrodes are avoided.Also, a seal for the adjusting device is obviated by the fact that themotor therefor is located inside the adjustment chamber. The concept ofthe adjustment chamber together with the fact that the coolant issubjected to the operating pressure in the arc combustion chamber resultin the further advantages, that the supply lines for coolant andelectric supply current to the displaceable electrode need not have arigid wall construction nor be displaceably passed through theadjustment chamber wall, but rather, flexible hoses can be employed withrigid lead-ins or fittings in the wall, and together they avoid the useof any displaceable sealing against high pressure.

In accordance with further features of our invention, the electrodes areconstructed as substantially cylindrical rings disposed in axialalignment opposite one another and containing magnetic coils,respectively, which rotate the arc during operation of the plasmaburner. The magnetic field produced by the magnetic coils is brought inthe region of high inductance t0 the lowpoints of the arc.

In accordance with an additional feature of our invention, a supply mainor manifold for working gas is provided leading to a location betweenthe electrodes. Depending upon requirements, the supply manifold canextend tangentially, radially or axially to the flow discharge nozzleand opposite the direction of flow discharge through the nozzle.

According to other features of our invention, the pressure transmitteris a pressure-equalizing or balancing vessel to which the pressure lineis connected from above and a coolant line from below. Instead of apressure-equalizing vessel, the pressure transmitter can be in the formof a piston in the pressure line.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin high-pressure plasma burner, it is nevertheless not intended to belimited to the details shown, since various modification and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

- The construction and method of operation of the invention, however,together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of a high-pressure plasma burnerconstructed in accordance with our invention;

FIG. 2 is a schematic view of a flow system including a pressuretransmitter, coolant circuit and pressure lines from the plasma burnerof the invention to the pressure transmitter.

Referring now to the drawings and first, particularly to FIG. 1 thereof,there is shown the burner proper of the high-pressure plasma burner ofour invention, formed of an arc chamber 1, an adjustment chamber 2, aburner head 3 and a nozzle member 4, carrying a flow discharge nozzle 5which, as shown, is in the form of a Laval nozzle. The are chamber 1 hasan inner operating space 6 connected through a pressure line 7 and apressure transmitter 8, in the form of a piston located in the line 7,with coolant in a tube 9 of a coolant circuit. A fixed electrode 10 anda displaceable electrode 11 are contained, at least partly in theoperating space 6 of the arc chamber 1. Both electrodes 10 and 11 are inthe form of substantially cylindrical rings and are axially alignedopposite one another.-The-electrodes l and 11 contain respectivemagnetic coils 12 which are excited during operation so that acusp-field is formed permitting the electric arc, which forms betweenthe faces 13 of the electrodes and 11 to rotate. To supply electriccurrent to the electrode 10, a terminal 14 is provided, and to theelectrode 11, a supply tubelS through which coolant is simultaneouslysupplied, is provided. A profile ring 16 of insulating material, forexample epoxide resin reinforced with glass fibers separates thepotential of the fixed electrode 10 from that of the displaceableelectrode 11. Thus, the walls of the arc chamber 1 and the adjustmentchamber 2 are insulated from one another at the flanged junction 70thereof. It should be noted that the flange bolts 71 are provided withinsulating bushings 72 and washers 73 so as to supplement the insulatingeffect of the ring 16.

The adjustment chamber 2 is in pressure equilibrium with the arc chamber1 through peripherally distributed intercommunicating bores 17, formedin a support plate 20, located between the chambers 1 and 2. For theself-same purpose, hose connections can be provided at the outer wallsof both chambers 1 and 2 so as to interconnect therein. The adjustmentchamber 2 is formed in essence by a peripheral chamber wall 18, abaseplate l9 and the support plate 20 which acts as a closure plate. Theelectrode 11 is displaceably mounted in the support plate 20. A remotelycontrolled motor 21 located within the adjustment chamber 2 and providedwith a gear transmission 74 drives an adjusting device for displacingthe electrode 11. The motor 21 thus rotates a spindle 22 suitablymounted in bearings, provided in the baseplate 19 and the supp'ort plate20 of the adjustment chamber '2 so as to be disposed parallel to theaxis of the chamber2, and thereby reciprocates a nutlike adjusting head23 along the spindle 22. Since the adjusting head 23 is fixed to theelectrode 11, the

latter is displaced therewith. The current supply tube and 4 anadditional nonillustrated connecting tube for discharging coolant extendrigidly through the baseplate 19 The supply tube 15 passes through aflush fitting 24 rigidly secured in an opening formed in the baseplate19. An observation window 25 is also provided inthe baseplate 19 forobserving the arc formed during operation of the plasma burner of ourinven-- tion, and for this purpose, the displaceable electrode 11, isconstructed so that it is open at both ends thereof, whereby a viewer atthe window 25 can see through the electrode 11 in the axialdirectionthereof. The supply tube 15 is connected to an end of a flexible hose27, which is connected at its other end to the electrode 11 andcommunicates with the interior of the casing 33 thereof for supplyingcoolant thereto. A brush or current collector 26 carried by theelectrode 11 is in sliding engagement with the rigid supply tube 15 soas to draw current therefrom as the electrode 11 is displaced in theaxial direction of the adjustment chamber 2.

The are chamber 1 is formed of axially aligned cascade rings 28,suitable bolted together, as shown at 75, the support plate and thecasing 33 for the fixed electrode 10 which forms a closure plate 29. Theclosure plate 29 provides the electrical connection between theelectrode 10 and the terminal 14.

The burner head 3 is formed primarily of an assembly casing 30, spacerwalls 31 and a faceplate 32. The nozzle member 4 is mounted on thefaceplate 32.

The pressure-stressed outer parts, such as the cascade rings 28, thechamber casing 18 and the assembly casing 30, can be formed of rust-freestainless steel. The parts that should be electrically conductive, aswell as the especially heat-stressed and cooled parts such as theelectrodes 10 and 11 and the electrode casings 33, are advantageouslyformed of copper.

At the burner head 3, coolant is introduced through the bore 34 andtraverses the space between the closure plate 29 and a spacer wall 31,as well as the space between the electrode casing 33 and the magneticcoil 12 and then flows through the space between the faceplate 32 and aspacer wall 31 and discharges therefrom through a bore 35. Additionalcoolant channels can be constructed in the cascade rings 28 of the arcchamber 1. Coolant connectors 36, shown broken away, areprovided for themagnetic coil 12 proper of the dismagnetic coil 12 proper of the fixedelectrode 10. The nozzle 5 is supplied with coolant through connectors38.

Working gas is introduced in the illustrated embodiment of FIG. 1,through a supply main or manifold 39 as well as through subsidiary lines40.

In the schematic flow system of FIG. 2, a pressure line 7 leads from aplasma burner 41, having the construction, for example, of theplasma'burner of FIG. 1, to an elevated equilibrium or balancing vessel8 and is connected thereto from above.'The pressure-equalizing vessel 8serves as pressure transmitter and subjects the coolant in the coolantloop 9 to the operating pressure in the inner space 6 of the arc chamber1, the coolant loop 9 being connected to the pressure-equalizing vessel8 at the bottom thereof. As illustrated in FIG. 2, the equilibriumvessel 8 is provided with a conventional overpressure safety valve 42and a conventional liquid level control 43. The liquid level control 43shuts off the supply of coolant when the proper level thereof isattained in the vessel 8 as it is filled for operating state, and theinstant during operation, that the liquid level'drops below a minimumliquid level in the pressure-equalizing vessel 8, as can occur due toloss of coolant from leakage, it shuts off the entire system. v i

The coolant loop 9 includes connecting lines 44 for the circulating pump45, a distributor line or manifold 46, individual coolant branch lines48 to 53, a collecting main or'manifold 47 and a return flow line 62.The branch line 48, for example is connected to the displaceableelectrode 11, the branch line 49 to the fixed electrode 10, the branchline 50 to the magnetic coil 12 of the displaceable electrode 11, thebranch line 51 to the magnetic coil 12 of the fixed electrode 10, thebranch line 52 to the cascade rings 28 of the arc chamber 1, and thebranch line 53 to the flow discharge nozzle 5. v

As shown diagrammatically in FIG, 2, various control valves 54,"flowrate meters 55 and temperature measuring devices 56, such asthermocouple devices for example, are provided in the branch lines 48 to53. They serve for determining the power delivered to the coolant andwhich is a function of the flow through-put rate and temperaturedifferent between inlet andoutlet of the respective branch cooling lines48 to 53.

From the difference to the expended electrical power, the power given upto the working medium or the eff ciency is determinable. i i I In orderto recool the coolant, in the illustrated embodiment of FIG. 2, a heatexchanger 57 having a circulatory loop 58,'as well as a heat exchange 59having a fresh water supply line 60 are suitably provided for thecoolant flow loop 9. The freshwater supply through the line 60 iscontrolled by a valve located in the line 60 in accordance with thereturn flow temperature of the coolant in the line 62 of the coolantloop 9, as measured by a thermocouple temperature-measuring device 61. i

' At an operating pressure of 50 atmospheres excess pressure in the arcchamber 1 and a discharge flow nozzle 5 of 3mm. diameter at itsnarrowest location, the pump power in the coolant loop 9 can be 10atmospheres excess pressure. The coolant water pressure upstream of thecirculating pump is then 60 atmospheres excess pressure and, downstreamof the circulating pump, it necessarily drops to about 50 atmospheresexcess pressure due to flow friction. For such an embodiment of ourinvention, the plasma burner power can be 500 kw and the throughput orflow-through 'rate of working gas can be 50 grams per second.

We claim:

1. High-pressure plasma burner of the gas heater type comprising apressuretight arc chamber, first electrode means mounted in said arechamber, second electrode means located adjacent said first electrodemeans, means for energizing said first and said second electrode meansso as to form an electric arc therebetween in said are chamber, flowdischarge nozzle placeable electrode being axially displaceable for agiven distance and serving as closure plate for closing an adjustmentchamber having a length corresponding to the given distance over whichsaid displaceable electrode is adjustable, said adjustment chamber andsaid arc chamber being in equal pressure communication with one another,motor-driven adjusting means in said adjusting chamber for adjustablydisplacing said displaceable electrode, and supply line means passingrigidly through a wall of said adjustment chamber.

3. High-pressure plasma burner according to claim 1,

wherein said electrodes are constructed as substantially cylindricalrings disposed in axial alignment opposite one another and containingmagnetic coils, respectively.

4. High-pressure plasma burner according to claim 1, including a supplymanifold for working gas leading to a location between said electrodes.

5. High-pressure plasma burner according to claim 1, wherein saidpressure transmitter comprises a pressure- I equalizing vessel, saidpressure line being connected to said pressure-equalizing vessel fromabove, and said coolant loop being connected to said pressure-equalizingvessel from below.

6. High-pressure plasma burner according to claim 1, wherein saidpressure line connects said are chamber and said coolant loop and saidpressure transmitter comprises a piston located in said pressure line.

1. High-pressure plasma burner of the gas heater type comprising apressuretight arc chamber, first electrode means mounted in said arcchamber, second electrode means located adjacent said first electrodemeans, means for energizing said first and said second electrode meansso as to form an electric arc therebetween in said arc chamber, flowdischarge nozzle means for discharging from said arc chamber working gasheated and ionized therein by said arc, coolant channels formed in partson said arc chamber thermally stressed by said arc, said coolantchannels being connected in a closed coolant loop, and a pressuretransmitter with a pressure line pressure transmittingly interconnectingsaid pressuretight arc chamber and said closed coolant loop. 2.High-pressure plasma burner according to claim 1, wherein at least oneof said electrodes is displaceably mounted for varying the spacingbetween said electrodes, said displaceable electrode being axiallydisplaceable for a given distance and serving as closure plate forclosing an adjustment chamber having a length corresponding to the givendistance over which said displaceable electrode is adjustable, saidadjustment chamber and said arc chamber being in equal pressurecommunication with one another, motor-driven adjusting means in saidadjusting chamber for adjustably displacing said displaceable electrode,and supply line means passing rigidly through a wall of said adjustmentchamber.
 3. High-pressure plasma burner according to claim 1, whereinsaid electrodes are constructed as substantially cylindrical ringsdisposed in axial alignment opposite one another and containing magneticcoils, respectively.
 4. High-pressure plasma burner according to claim1, including a supply manifold for working gas leading to a locationbetween said electrodes.
 5. High-pressure plasma burner according toclaim 1, wherein said pressure transmitter comprises apressure-equalizing vessel, said pressure line being connected to saidpressure-equalizing vessel from above, and said coolant loop beingconnected to said pressure-equalizing vessel from below. 6.High-pressure plasma burner according to claim 1, wherein said pressureline connects said arc chamber and said coolant loop and said pressuretransmitter comprises a piston located in said pressure line.